Definition
A simple approach lighting system used at non-precision instrument runways, consisting of seven omnidirectional flashing lights — five spaced along the extended runway centerline outward from the runway threshold, and two more positioned on either side of the runway threshold itself. The lights flash in sequence from the outermost light toward the runway, helping the pilot identify the runway and align with its centerline during the final stages of an approach.
Plain English
A row of flashing lights leading up to the runway that helps a pilot find and line up with the runway when approaching to land, especially in poor visibility. The lights flash one after another toward the runway, like an arrow pointing the way in.
Context Anchor
Seen on instrument approach charts, airport lighting legends, and in notes about approach lighting systems or inoperative lighting components.
Derivation
‘Omnidirectional’ comes from Latin omni- meaning ‘all’ and ‘directional’ from directio meaning ‘a pointing.’ The lights are called omnidirectional because each one can be seen from any direction, not just from straight down the approach path. This matters because pilots flying a circling or offset approach can still see the lights and use them to find the runway.
Why Pilots Care
The operational status of ODALS directly affects landing minimums and whether an approach may be continued when visual references are required.
Grounding Statement
Picture a short trail of flashing lights leading toward the runway, with two lights near the point where the usable runway begins.
Intuition Check
“Omnidirectional” does not mean you may approach the runway from any direction. It means the lights themselves are visible from many directions.
Example Sentence 1
The chart noted that ODALS was the only approach lighting available, so the crew briefed the higher visibility minimum before starting the approach.
Example Sentence 2
With the ODALS inoperative, the approach minimums increased and an alternate procedure was required.